Field of the Invention
The present invention relates to an image stabilization apparatus to, for example, reduce blurring of a subject image and an optical device.
Description of the Related Art
Some lens barrels of digital cameras or the like have an image stabilization apparatus that reduces blurring of a subject image, which is formed on a light-incident surface, by moving all or a part of a shooting optical system in response to externally-applied vibration.
For example, for an image stabilization apparatus constructed such that a movable unit which holds a corrective lens moves on a plane perpendicular to an optical axis, there has been proposed a technique to set a range over which a restriction unit restricts movement of a ball sandwiched between a fixed unit and the movable unit to a half of a maximum amount of movement of the movable unit.
According to this proposal, when the movable unit lies at a central position, the ball is allowed to move without coming into contact with the restriction unit while the movable unit is moving as long as the ball lies near the central position. When the ball is off the central position, the position of the ball when the movable unit lies at the central position falls within a predetermined range near the central position by carrying out a resetting operation to bring the ball back to the central position (see Japanese Patent No. 3,969,927).
Japanese Patent No. 3,969,927 above is based on the principle that the amount of movement of the ball is a half of the amount of movement of the movable unit. However, in an image stabilization apparatus in which a movable unit which holds a corrective lens rotates about a rotational axis perpendicular to an optical axis, not on a plane perpendicular to the optical axis, a ball sandwiched between a fixed unit and the movable unit moves on a spherical rolling surface.
In this case, the amount of movement of the ball varies with directions of the rotational axis, and hence in a direction of the rotational axis in which the amount of movement of the ball is small, the ball cannot be reset to a central position or its vicinity even by performing a resetting operation, and hence the range over which the ball possibly lies after the resetting operation is wide.
For this reason, assuming that a position of the ball when the movable unit lies at the central portion is an initial position, the range of the initial position is wide. When the range of the initial range is wide, an image stabilizing operation tends to be affected by the surface accuracy of a rolling surface for the ball, and performance of the image stabilization apparatus may be unstable.